Convert Human Age to Dog Years

Empirically, large and giant breeds age faster than small ones – a Great Dane is considered senior at 6, a Chihuahua at 10+. The standard veterinary chart reflects this: post-age-2, small dogs accumulate 4 human years per dog year, medium 5, large 6, giant 7. Cats don’t show this size-dependent pattern, which is why the cat version doesn’t have a size selector.

Myth. That rule came from rough averages and ignores the fact that puppies mature incredibly fast in year 1. The modern AVMA/veterinary scale has dogs reach the equivalent of a 15-year-old human by their first birthday, then slow down. That’s why this tool uses three phases, not a constant multiplier.

Four stages based on dog years: Puppy (0-1 dog year, rapid growth), Junior (1-2, adolescence and sexual maturity), Adult (2-6, stable adult), Senior (6+, age-related care considerations begin). The exact onset of Senior shifts by breed – giants hit it earliest.

30 human years → 3.5 dog years for a small breed, 3.2 medium, 3.0 large, 2.86 giant. All four are in the Adult stage – but the giant-breed result is closer to the Junior threshold because giant dogs age faster biologically.

Yes. The formula is piecewise-linear, so 30.5 years gives you a continuous answer (3.3 medium-breed dog years). Useful for modeling life transitions at specific ages.

We convert your human age to dog years, then convert it back using the same size. A 30-year-old medium-breed human round-trips to exactly 30. It’s a sanity check – if the number drifts, there’s a bug (there isn’t; the formula is mathematically invertible).

No. Everything runs in your browser – three divisions, a couple conditionals. No fetch, no XHR, no analytics. Open DevTools → Network and watch nothing after the initial page load.

Yes. Total bundle is under 20 KB (HTML + CSS + JS). Load once, disconnect, keep calculating. Works on flights, trains, and air-gapped machines.

Use the companion Dog-to-Human Age converter in the same Time category. That’s the more common ask (“how old is my dog in human years?”). Both tools use the same formula and breed-size divisors, so the round-trip is exact.

Approximate. Veterinary sources often cite the cutoffs as 10 kg (small/medium), 23 kg (medium/large), 45 kg (large/giant) – which matches AVMA guidance. Borderline breeds (e.g., a 24 kg Border Collie) can reasonably use either medium or large; try both and take the midpoint.